Abrasive wheel and method of making the same



Jan. 2l, 11936. A R. c. BENNER. AL y 2,028,183

' ABRAsIvE WHEEL AND METHQQOE MAKING 'THE SAME Filed April 1a, 195o 2 sheets-sheet 1 Fiyi.

INVENTORS myn.; chem fin van. QAM-l 'ATTORNEY Jan. 21, 1936. R. C. BENNER Er AL 2,028,183

ABRASIVE WHEEL AND METHOD OF MAKING THE SAME Filed April 18, 1930 2 SheetsSheet 2 INVENTORS l Patented 21, 1936` UNITED STATES;

' amuse ABaAsIvE WHEEL AND METHOD or MAKING THE' SAME vRaymond Calvin Benner -and William George Soley, Niagara Falls, N. Y.,`assignors to The Carborundum Company, Niagara Falls, N. Y.,

a corporation of Pennsylvania Application April 1s, 1930,serial No. 445,361

Canada June 7, i929 16 Claims.

" 'l'his invention relates to an improvement in -@abrasive wheels and the method'of making the same. It pertains to the strengthening of abrasive wheels of bonded granular abrasive material by the additionof a member or members that reinforce the wheel against the stresses incident to operation at high peripheral speeds.

. Itis common practice in industry to operate grinding wheels at peripheral speeds of 5500 feet 10. per minute and greater.` Centrifugal forces set 'up stressesrin grinding wheelsvrotating at such ,speeds that frequently lresult in wheel breakage, particularly if the wheel is subjected to other stresses resulting from such causes as elevated temperature, impact from the application of the work, or torsion-,from heavy loading. Centrifugal stresses must be seriously considered in the operation of grinding-wheels since they increase in magnitude as the square of the velocity. Various means have been employed to reduce breakage or to provide greater safety in cases of breakage. The wheels have been made thicker at the arbor hole or center and tapered toward .the periphery in order to permit driving anges g5 of con'iparable conca'vity to hold the pieces in case of breakage. ing of soft rubber have been interposed between the wheel and each driving ange' in order to provide a cushion that will restrain pieces from flying out when the wheel breaks. i These latter rubber coated metalplates have been attached to the sides ofthe wheel by means of a soft rubber cement and also have been applied to the wheel by the clamping action of the anges.

` Each of these methods is effective to a certain degree in holding ythe pieces after breakage occurs, but none of them are materially effective in preventing breakage. 7We have found that the bursting speed of abrasiye wheels can be greatly increased by attaching o one or both faces of the wheel a reinforcing ember that reduces the tendency of the wheel .to expand when itis rotating.

In the drawings:

5. Figure 1 shows' a cross-section through a diameter of a wheel reinforced by. two lateral members.'

Figure 2 is. a view in elevation partly broken Y away to. Ashowthe metalV elements `of a lateral reinforcement.

Figure 3 shows a crossfsectional view along the line III-III of Figure 2.l

Figure 4 is a view in elevation that shows one type of metal member in position' on the wheel to'receivethe embedding 'I'hin metalplates with a coatl in diameter (ci. 51-168i Figure 5 is a view showing a wheel with a metal plate attached to its face.

Figure 6 is a cross-sectional view along the line VI-VI of Figure 5; and

Figure '7 is a cross-sectional view ofa reins forced wheel moimted and ready for operation.

The wheel I illustrated in Figure l comprises an abrasive member 2 with two intimately attached reinforcing members (3) (3). The rein' bers 5 embedded in an adhesive medium 6. 'Ihe 15 members 5 are shownv as Jrings .of circular crosssection but other cross-sectional shapes or other forms than rings may be used. Figure 4 shows a metal member 'I in the form of a spiral, while in Figures 5 and 6 is shown a 20 metal disk 8 having concentric grooves 9 in one of itsfaces.4

'I'he assembly shown partly in section in Fig-- ure 7 illustrates the method of mounting the wheel for use. In this figure the wheeli com`- 25 prising the abrasive member 2 with reinforcing' members 3" and 3" is centered on the shaft Ill by means of a bushing l of soft metal, such as lead or babbitt,' or of wood. The wheel I is held against the flange I I, which-bears on the shoulder 30 Il, by means of a flange I3, which4 is drawn up by the nut |41 One way of providing greater strength in the wheel involves the use of members that are intimately united to the abrasive and-are more 35 rigid than the bonded abrasive member. By this means some of the stresses set up in the abrasive wheel by centrifugal force -are,-at least in effect,

`transferred to, and borne by, the reinforcing member or members with the result that the 40 tendency of the abrasive wheel to expand in diameter is lessened. If the member that is inti- Amately united to the abrasive wheel not only is rigid enough to bearpart of the stress that tends to make the wheel expand but also normally exerts a contractile force inwardly of-the wheel, thislforce or stress will oppose the stresses caused by the centrifugal forces incident to ro' tation. 'I'his contractile force may be obtained in the reinforcement during-the application of -the reinforcement to the wheel under the action of heat by utilizing as reinforcements materials which may be effectively united with the` bonded abrasive and which will shrink more thanjtl'ie bonded abrasive does upon cooling. Naturally, the degree of difference between the shrinkage of the bonded abrasive and of thereinforcing member must be controlled to prevent breakage of the wheel. Our previously led applications bearing Serial Numbers 313,087 and 336,557,'of which the present application is a continuation in part, disclose this subject matter.

It may be statedthat, in general, the greater the degree of difference between the shrinkage of the reinforcement and that of the bonded abrasive the greater will be the strengthening effect of the reinforcement upon the wheel; how- I ever, the difference may be great nough to cause the reinforcement to fracture by choosing a reinforcing member that will produce the maximum stress consistent with freedom from fracturing the wheel. Because of the large number of bonded abrasive compositions,

each composition having particular physicalcharacteristics, it is not practicable to make a' specific statement dening the material that will provide maximum reinforcement without undue undue stresses.

stress for each bonded abrasive. The reinforcingmaterial preferably is `chosen for vone particular abrasive composition.

The choice of the material or materials for the reinforcement of any particular bonded abra-- sive composition' involves apnumber of factors,

among which are the coefficients of thermalexyyolved in the choice of a reinforcing body that will' provide the maximum reinforcement without The effectiveness of the reinforcement depends also upon the aging characteristics of the bonded abrasive and the rein-` forcing body. Aneviation of the strom. oaused by the shrinkage of the reinforcement decreases the strengthening effect of the reinforcement, and

weakening of thebonded abrasive under continued strain reduces the allowable strain consistent with safety from undue stresses.

Because of the number of factors involved and because of the interdependence of vthe physical form' and properties of one material upon those of the other material or materials, the absolute determination of the suitability of a particular combination of materials by calculation, is ditllcult and in some cases at least a practical'impossibility. We first determine the probablesuitability' from thelphysical characteristics of the material and then we provide maximum reinforcement consistent with. freedom-from undue stresses by experimentation.

In the preliminary choice of the reinforcement.

we are guided by two of the characteristics of the material in addition to its strength. These are its coefficient oi'. expansion audits modulus of elasticity. A material that has a low modulus f elasticity, withfrespect to that of the bonded abrasive, may have a relatively'high coeicient of expansion. Buta material that has arelatitely high modu1us of elasticity should have, in general;- only a moderately higher coeicient of expansion than that of the bonded abrasive.'

-We have'found that the characteristics of hard rubber c'an be modied to adapt it -to bonded e wheel uponv cooling. We provide against such a contingency abrasive articles of different coefficients of thermal expansion. A typical example is f Parts Rubber n u 10 5 Sulphur- 2.5 SiC-500 mesh which, when cured to the full extent possible with that'proportion of sulphur, has been found satisfactory as a reinforcing material for a medium l0 grade wheel of a specific type of bond and abrasive but not necessarily for others.

It has, approximately, a coefficient of thermal expansion of 20 106/C, a modulus .of elasticity -of 1.5 106#/in2 and a tensile strength of 2,000 l5 pounds per square inch. f`

The following specific methods of applying reinforcements are given by Way of illustration and l are not intended to limit the invention to the specific materials or manipulative details dis- 20 closed, nor are they intended to limit the process f to the specific steps-or sequence of steps.

The abrasive surfaces that are to 'receive the reinforcing members are rst primed with the rubber compound softened with a volatile soften- 25 er such as benzol. The ratio ofbenzol to rubber compound may be varied as required, but it has been found that 2 parts of benzol and 1 part of the above rubber compound form. a priming /material that may be applied easily by brush- 30 ing and leaves a satisfactory coating of rubber compound on the abrasive surface after the solvent has evaporated. If a thicker coating of rubber compound than that produced by one application, either by brushing or by spraying, is 35 desired, additional coats of the solvent-softener compound may be applied. Sufllcient time should elapse between coatings to permit the solvent to evaporate completelybefore a subsequent coat is applied. J l Y 40 A sheet of the rubber compound, approximately V8 inch thick, is then applied to each of the primed surfaces of the abrasive wheels and-is cured by heat and pressure. The wheel with a sheet of the rubber compound on each of its side 45 faces is then subjected to a uniform pressure of approximately 30 lbs. per square inch, and while thspressure is maintained-is heated to approximately 320 F.

When the curing is completed the wheel cooled slowly, for example, at a uniform rate to l room temperature in 2 hours. l

VThe reinforcements hereinbefore .described are of the type that wearI away as the wheel wears `away. This feature is of importance, particular- .ly in those applications that do not permit stopping the wheel to remove a portion ofthe reinforcement when the abrasive has worn to the diameter of the reinforcement. 60 Oneh method of embedding the metal element or elements in the adhesive portion of the reinforcement comprises the use of two comparatively thin sheetsof rubber 'compound instead of one relatively thick sheet. ABy this means a sheet of rubber may'be applied to eachwheel and the metal part or parts may be inserted between the coated faces of the wheels and another sheet of rubber compound.y The curing operation is carried out as described above. .(0

Qne method of providing a wheel of the type f illustrated in Figures 2 and 3 comprises priming the abrasive fabes'with a plastic material consisting of, by way'of example, 22% phenolic condensation resin in the B stalla-68% finely divid- 75 ed inert material, such 220 meshA silicon carbide, and 10% of a solvent or plasticizer, such as furfural. 'I'his priming coatis worked into the san putty knife er other suitable instrument m order to provide good contactbetween the plastic material and the bonded abrasive. The primed surface then vis `covered with plastic material. Continuous steel rings of the desired cross-sectional area and diameter then are pressed into the plastic material in concentric relationship to the wheel and to each other. and covered with plastic material. Y

The plastic material is then cured under pressurface pores of the abrasive face by means of a sure at a temperature that is consistent with the requirements 'of the particular material used and that will -not set up undue stresses in the bonded abrasive. When the curing of the reinforcement is complete the wheel is cooled slowly toordinary temperature. A uniform temperature drop of 2 F. per minute has been found satisfactory, and is given by way of example.

The reinforcements shown in Figures 2, 3, 4, and 6, which comprise metal elements joined to the bon'ded abrasive, do not w'ear away during the normal operationof the wheel. Withvthe particular form of metal elements shown in Figures 2 and 3 reduction in size of the reinforcement is accomplished by removing one or more of the outer metal rings as required? 'I'his is donev by cutting out or chipping outI theV embedding material and prying oif the desired number of rings. The same general procedure is followed in reducing the number of turns inthe spiral 1 'of Figure 4. The plate 8 of -Figures 5 and 6 is reduced in diameter by cutting through the outermost band with a chisel and then-removing said band by means of a slotted key. The band of metal is rolled up on the end of the key as it is torn from the wheel. I

While the methods described above have been" applied specifically to particular modifications as illustrated in .the drawings, it will b e recognizedby those skilled in the art that the description applied to one illustratiorfmay be applied .to another of the illustrations or to modifications not shown in the drawings.

Having thus described our invention, whatwe claim is:

1. An abrasive wheelI having a metal disk of substantially' the same diameter as the abrasive wheel attached to each lateral face of said abrasive wheel by a hard rubber composition.

2. A reinforced wheel of bonded abrasive material having reinforcing members which elongate less than the abrasive material does under the same stress, saidV members comprising metal rings embedded in a cement which adheres rigidly to the bonded abrasive, the elasticity of thecement being of a similar order4 of magnitude to that of the bondedabrasive. s 3. An abrasive wheel construction including an abrasive wheel body and convolutions of wire secured to a face of the wheel, said convolutions being bonded to the face of the wheel by .a layer of tough, plastic material cured or indurated under pressure. i

4.'An abrasive wheel having a lateral reinforcing member of vulcanized hard rubber com. lpound intimately united-to a side thereof, said abrasive wheel being u nder a compressive stress directed inwardly toward the rotativa axis of the wheel and .said lateral facing being under a ten.-

sile stress.

stress.

c 3 5. In the manufacture of abrasive wheels, the method of reinforcing the same against the centrifugal stresses of rotation which comprises mixing rubber and sulphur with a filler to provide a 4 plastic composition which will cure t o a solid with a coefficient of thermalexpansion higher than but of the same, order of. magnitude as that of the abrasive wheel, coating the lateral faces of thel of the wheel'and said lateral facings being under a tensile stress. g

7. In the manufacture of abrasive wheels, the method of reinforcing the same against the centrifugalstresses of rotation which comprises mii:-

ing a heat hardenable organic plastic material with a filler toprovide a plastic composition which will cure to a sblid with a coemcient of thermal expansion higherthan but of the same' -order of magnitude as that of-the abrasive wheel,

coating the lateral'faces of the abrasive with said plastic composition, heating the 4thus coated abrasive wheel to cure the plastic material, `and cooling the same after the plastic material has been cured, whereby the abrasive wheel will be subjected to a' compressive stress directed toward its rotative axis and said lateral coatings will be subjected to a tensile stress.

8. In the manufacture of abrasive wheels, the method of reinforcing the same against the centrifugal stresses of rotation which comprises mixing a phenolic condensation resin with a filler to provide a plastic composition which will cure to .a solid'with a coefficient of thermal expansion higher than but-of the same order of magnitude as that of the abrasive wheel; coating the lateral faces of the abrasive with said plastic composition, heating the thuscoated abrasive wheel to induratc the plastic material, and cooling the same after the plastic material has been cured, whereby the abrasive wheel will be subjected to a compressive stress directed toward its rotative axis and said lateral coatings will be subjected to a tensile stress.

9. An abrasive wheel having a metal disk ate tached to each lateral face thereof by cement containing a phenolic condensation resin and granulated ller in suiiicient proportion to modify the character of the resin whereby the said cement has a higher modulus of elasticity than the said abrasive wheel.

l0. An abrasive member-having an abrasive body of bonded abrasive grains, arigid backing.

support therefor, and an intermediate, layer of hard rubber containingat least twenty per cent by weight of sulphur vulcanized therebetween and permanently securing the abrasive body and backing support together as an integral unit.

l1. An abrasive lwheel having a reinforcing member comprising a metal disc and a body of hard rubber compound intimately united to a lateral face of the said wheel by intimate union of the said rubber compound with the said lati eral face of the wheel and with the said metal disc. Y

12. An abrasivewheelI construction including an abrasive Wheel b ody and a reinforcing-member; comprising an intimate mixture of organic ma- A terialand granulated ller intimatelyunited to a side ofthe said wheel whereby .the strength of the said reinforcing member supplements the strength of the said abrasive wheel body, 4said mixture havinga coefficient of expansion and a modulus of elasticity of the same order of magnitude but higher than those of thev abrasive Wheel body. f

13. An abrasive wheel construction including an `abrasive wheel body and a reinforcing member Vcomprising an intimate mixture of organic material and granulated ller intimately united to a side vof the said wheel whereby the strength of the said reinforcing member supplements the strength of the said abrasive wheel body,. said reinforcing member having a modulus of elasticity of the same order of magnitude but higher than that of the abrasive lwheel body whereby the abrasive wheel construction is .capable of withstanding greater centrifugal stressl than the abrasive wheelibody alone. J-

14. An `abrasive wheel construction including Y an abrasive wheel body and a reinforcing member comprising an intimate mixture of indurated synthetic resin and granulated filler in suflcient. proaoasass Y l portion to modify the character of the resin whereby the said reinforcing member has a higher modulus of elasticity than the said abrasive wheel body, the said reinforcing member being intimately united to the said abrasive wheel body whereby the strength of the reinforcing member supplements .the strength of the said abrasive ,wheel body.v y

15. An abrasive wheel construction including an abrasive wheel body and a reinforcing member comprising an intimate mixture of indurat, edv phenolic condensation resin and granulated filler in suicient proportion to modify the character of the resin whereby the said reinforcing member has a higher modulusof elasticity than 

